1. Field of the Invention
The present invention relates to a method of reducing the error rate of a magnetic recording medium having a non-magnetic support member on which a magnetic layer composed of a metal magnetic thin film is formed.
2. Description of Related Art
Conventionally, in order to achieve a high image quality in the field of video tape recorders (VTRs) and the like, there has been the widening demands for high density recording of magnetic recording media. Therefore it is important to perform a further shorter wavelength recording.
On the other hand, digital magnetic recording systems are aiming at a higher density recording, and a magnetoresistance effect type magnetic head (an MR head) of high sensitivity and a giant magnetoresistance effect type magnetic head (a GMR head) have been applied. However, in order to reduce error rate, it becomes necessary to realize a high output and a high CNR, while reducing dropout (D.O.) that is a signal regeneration defect.
It is also important to have a waveform distortion in accordance with the characteristic of a magnetic system, in order to reduce error rate. Usually, the system determines the optimum value of reading timing in accordance with the characteristic of a magnetic recording medium. For example, a magnetic recording medium, a magnetic layer of which is formed by oblique evaporation of Co, has an easy axis of magnetization located at about 30° with respect to the direction of a plane of the magnetic layer. Therefore the reading timing is usually determined in accordance with the occurrence of a 55 to 60% waveform distortion.
In view of the above, proposals have been made to specify a half-width on the basis of magnetic property (see, for example, Japanese Patent Application Publication No. 2002-92853), which merely presuppose dependence on a magnetic recording system. No consideration has been given to the fact that the essence of half-width is a matter to be determined when used in a magnetic recording system.
Hence, the conventional designs of magnetic recording media have been required to reduce D.O. and control wavelength distortion to a proper value, while achieving a high CN ratio. Even if a low D.O. and a high CN ratio are achieved, it is not yet enough to reduce the error rate of a magnetic recording medium having a tendency toward a further higher performance.
While in the recent years, as the need for still higher image quality has been increased, the electromagnetic characteristic of magnetic recording media has been improved. There is a proposal of a digital VTR system using a narrow tape having a width of 8 mm or less, for example.
Also in recording media for computer, a tape of ½ inch or less has been proposed to perform recording/reproducing at a higher density.
However, such a narrow tape is also required to have a high electromagnetic characteristic to ensure a sufficient recording density. In the present circumstances, only thin-film type magnetic recording media such as evaporation tapes can comply with this need. Further, in order to comply with a higher density recording, it seems to be essential to use a magnetic recording medium suited for an MR head and a GMR head that have a higher sensitivity and a high output.
Heretofore, it was considered that a medium having a low error rate is achievable by sufficiently suppressing D.O., achieving a high output and a high CN ratio, and controlling wavelength distortion to a desired range. However, it is important to further reduce error rate of a medium in order to achieve a further higher density.